Defining a target of stacked 2d spheres

[ChetnaPH]

Hi! Can you please help in defining a different 2d target geometry. I want to define small 2d spheres one below the other in a vertical line.
It'll be a great help!

[Status-Mirror]

Hey @ChetnaPH,

We can do this using by building a density in the species block, using expressions given in the maths parser.

I have included a simple input deck and a density plot which shows how this can be initialised. Here, I have used a series of lines to say that if we are in cells within the radius of a particular circle, set the density to the desired value, otherwise do not change the density of the species. This way we can build up the target one circle at a time. If you have many circles, you may want to automate the generation of this text.

begin:control
  nx = 300
  ny = 600
  x_min = 0
  x_max = 30.0e-6
  y_min = 0
  y_max = 60.0e-6
  t_end = 1.0e-15
end:control

begin:boundaries
  bc_x_min = open
  bc_x_max = open
  bc_y_min = open
  bc_y_max = open
end:boundaries

begin:constant
  r0 = 3.0e-6       # Sphere radius
  x_cent = 15.0e-6  # Centre of sphere line in x
  den_e = 1.0e20    # Sphere electron density
  
  r2 = r0^2
end:constant

begin:species
  name = electron
  mass = 1
  charge = -1
  npart_per_cell = 50
  
  density = 0
  density = if ((x - x_cent)^2 + (y - 1.0*r0)^2 lt r2, den_e, density(electron))
  density = if ((x - x_cent)^2 + (y - 3.0*r0)^2 lt r2, den_e, density(electron)) 
  density = if ((x - x_cent)^2 + (y - 5.0*r0)^2 lt r2, den_e, density(electron)) 
  density = if ((x - x_cent)^2 + (y - 7.0*r0)^2 lt r2, den_e, density(electron)) 
  density = if ((x - x_cent)^2 + (y - 9.0*r0)^2 lt r2, den_e, density(electron))  
  density = if ((x - x_cent)^2 + (y - 11.0*r0)^2 lt r2, den_e, density(electron))
  density = if ((x - x_cent)^2 + (y - 13.0*r0)^2 lt r2, den_e, density(electron)) 
  density = if ((x - x_cent)^2 + (y - 15.0*r0)^2 lt r2, den_e, density(electron)) 
  density = if ((x - x_cent)^2 + (y - 17.0*r0)^2 lt r2, den_e, density(electron)) 
  density = if ((x - x_cent)^2 + (y - 19.0*r0)^2 lt r2, den_e, density(electron))
end:species

begin:output
  dt_snapshot= 1.0e-15
  number_density = always
end:output

[Status-Mirror]

I'm going to mark this issue as closed for now, but feel free to include any follow-up comments!

Cheers,
Stuart